This paper describes the use of clustering in ad hoc networks,
describes, very briefly, some key agreement schemes for clustered ad
hoc networks, and proposes how a combination of AT-GDH and the
Burmester-Desmedt group key agreement scheme can be applicable in
clustered ad hoc networks.

Technical
---------
Section 2.3
- BD takes two rounds, but each round is n broadcasts.  In that sense,
  the complexity is not constant, but O(n)
Section 2.4
- what is q? Is that the order of G? Is there a relationship between p
  and q?
- The range of f() is Z*_p, but the domain is Z_q (if q is the order
  of G).  How are the k values transformed so that f() can be applied
  again to the result of a previous f()? (The same question applies to
  Section 2.5 as well).
Section 6
- you make a good observation in the last paragraph.  A pre-requisite
  for AT-GDH spanning tree formation is that in each cluster, there is
  at least one node who is within 1-hop distance to a node in another
  cluster. How does this node decide which cluster it belongs to?
  Could a node be a member of all clusters that it is within 1-hop
  range of?
  -> an example showing how a particular clustering algorithm works in
     a particular network topology would help.
Section 6.1
- as above, if the complexity of BD is O(n), the complexity of
  Clustered AT-GDH will be O(n logn)
- Under what conditions does AT-GDH achieve O(log n) round complexity?
  (e.g., when the spanning tree is "balanced"?)

Editorial 
--------- 

In general, you need to give more descriptions of the schemes and more
examples. In the current state, it is difficult to convince the reader
of the claimed advantages of your scheme over others because (a) the
benefits of your scheme are stated, but not very well demonstrated,
and (b) the other schems are described very lightly.

Section 2.2
- s/take equally part in/take equal part in/
  (or "take part in equally")
- an acyclic connected undirected graph is an unrooted tree.  You need
  to define a rooted tree before moving to the next sentence.